A well may be drilled into the ground for a variety of extraction or exploratory purposes. By way of example, a wellbore may be formed to allow liquids such as water or petroleum, or gases such as natural gas, to be extracted therefrom. In yet other cases, a wellbore may be formed to obtain information about the physical properties of soil and rock in a particular area, or to explore for mineral or ore deposits.
Various drilling systems and mechanisms may be used to drill or otherwise create wellbores, which wellbores themselves may vary from a few feet to a few miles in depth. Particularly for long wellbores, mechanical drilling systems may be used to drill the wellbore. An example rotary drilling system may include a drill rig that uses a rotary table or top drive to rotate a drill string within the wellbore. The drill string can include a bottomhole assembly (“BHA”) that includes a drill bit. The BHA may in turn be coupled to a string of drill pipe that is rotated to provide torque to the drill bit. The drill pipe may also be hollow or have conduits therein to pass drilling fluid to and from the drill bit to cool the drill bit, convey cuttings to the surface, or for other purposes.
Whereas rotary drilling systems may rotate a drill string to provide torque to a drill bit, other drilling systems may operate in other manners. In a coiled tubing system, for instance, continuous, coiled tubing may be supplied from a spool that is located at the surface. An injector can grip the tubing and insert and withdraw the tubing from the wellbore. A BHA may be coupled to an end of the coiled tubing and inserted into the wellbore. The BHA may in turn include a motor that is used to rotate a drill bit. A motor may be driven by using drilling fluids that are pumped from surface equipment through coiled tubing or a drill string. The drilling fluid may flow downwardly toward the motor, and the motor may convert the axial flow of the drilling mud into a rotational force used to drive the drill bit located below the motor.